I'm reading a rather small book simply called 'Duchamp' by Janis Mink. The book offers a lot of great anecdotes on my favourite salt salesman (Marchand du sel).

Duchamp spent 3 months in München in 1912. Back then the town was a melting pot of decadence (remember Cabaret), satire (remember Georg Grosz) and avant-garde. Duchamp did speak a little German, so it is possible, even probable, that he went to see a show by Franz Wedekind.
After having served 9 months in prison for the publication in Simplicissimus of some of his satirical poems, he started a career in what some called the theatre of subversion. He became a 'moralist who wore the mask of an immoralist.' Wedekind was then (and still would it seems by todays standards!) a provocateur playing games with the repressed sexuality of his audience. In his first major play, "Frühlings erwachen" (Spring awakening), which dealt with a group of school children just entering the age of puberty, he used to ask every young woman in the room whether they were virgins and frequently used to piss and even pretended to masturbate on stage. there were references to homosexuality, suicide and abortion. Eat your heart out, G.G. Allin!
Wedekind started from the purity of children to show the real corruption in established society. The three main characters, Moritz, Wendla and Melchior become victims of the permeating hypocrisy. Today Wedekind is mostly famous as the playwright of "Pandora's Box", a tale of sexuality and violence brought to the silver screen by G.W. Pabst in 1929, starring a sublime Louise Brooks.
Here's a synopsis of his "Spring Awakening" .
It is highly probable that Wedekind was a major influence on the later dada performances.

During his stay in Germany, Duchamp also visited the village of Neufahrt where he might have visited the bizarre church of Wilgefortis.
Bizarre because of its legend: Wilgefortis was a virgin princess who refused every candidate her father had presented for marriage.
She finally got gang-raped. During her ordeal she prayed to God to disfigure her body and suddenly grew a Christ-like beard. So her father had her crucified (It's quite horrible, yet the slapstick scenery which shows up in my mind re-reading the above sentences had me LOL).
The church used to show her weird hermaphrodite statue. Actually in the early Middle Ages it was common to represent Christ in a long robe, which is probably the origin of this legend. Her feast day is July the 20th.
Wilgefortis might have been of some influence on Duchamps LHOOQ and on his character of Rrose Sélavy.

Another influence on Duchamp was French scientist Henri de Poincaré.
In 1913 Duchamp worked as a librarian in the Ste Geneviève library in Paris. A period in which he abandoned art entirely and studied the latest scientific breakthroughs. Poincaré was a major advocate of the upcoming agnosticism in science. One of his ideas might apply to Duchamp's later career as an artist: "Science cannot penetrate anything, save the relationships amongst things. Outside of those relationships there is no objective experience of reality".

The major influence on Duchamp though, which would pervade his entire work and life, for whom he had the utmost admiration, was one of the most bizarre French writers of all times, the dandy millionnaire Raymond Roussel.
Right now I'm also reading a study on Roussel's 'Impressions of Africa' by his most erudite scholar, Jean Ferry , an important member of the Collège de 'Pataphysique  who strangely pops up once in a while in MLA posts. I'll blog in him one day. Roussel often used homophony to write his stories: he started with a sentence, ended with a sentence which sounded the same but had a different meaning, and invented a story linking the two. Bust above all Roussel created a revolution in storytelling, in a similar vein as Sterne of Joyce, as many of his stories contain multi-levelled meanings. Inspired by Roussel Duchamp would often make works which referred to previous ones, and the titles of his works often used to have an even, if not greater, value as their object.

Another anecdote: mosbunall here remember that Duchamp used to live in a very small appartment (11, rue Larrey) and hence had a custom made door which could close alternatively different rooms. In the same vein, het used to have a bath in the middle of his living-room at 1947 Broadway in 1916 which he shared with Jean Crotti and his wife Yvonne Chastel. A rope hanging from the ceiling which he could pull to shut the main door whenever he was taking a bath. Actually the idea comes from a Buster Keaton movie which strangely appeared on my Facebook wall (by collector of mad writers Marc Ways) recently!